Three clones for structural genes coding for proteins secreted from the rat ventral prostrate have been identified by hybrid arrest translation. The three cloned inserts have been mapped with restriction endonucleases, and the homologous mRNAs have been shown to be induced by androgens. A rat gene library carried in Lambda phage charon 4A has been screened for the genomic seqences corresponding to two of the secreted proteins. Two signals have been purified from one million phage clones and the inserts subcloned into PBR325. A Cfo I fragment 5.2 kb has been characterized from both signals which codes for part of a 20,000 dalton secreted protein. Sequencing of this gene is underway. Human and rat ventral secretory proteins were compared by two-dimensional gel electrophoresis of human and rat prostate secretions. A major low-molecular weight protein is synthesized by both rat and human prostates and has similar but different molecular weight/isoelectric point coordinates (13,000/5.6 rat, 17,000/6.0 human). Homology of these proteins at the cDNA level is under investigation.